Insertion modes in an HTML parser may include instructions like "process
the token in the IN HEAD insertion mode." The rules do not change the
insertion mode of the parser, but the errors are triggered outside of the
rules for the current insertion mode. These will be misleading when
bailing on these instructions, because it will point someone to the wrong
place in the code to find the source of the error.
In this patch all of the bail-points due to lacking insertion mode support
are hard-coded to better orient someone to the section of the code lacking
support for handling the input HTML.
Developed in https://github.com/wordpress/wordpress-develop/pull/7043
Discussed in https://core.trac.wordpress.org/ticket/61576
Follow-up to [58679].
Props: dmsnell, jonsurrell.
See #61576.
Built from https://develop.svn.wordpress.org/trunk@58781
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